Issue 48, 2019, Issue in Progress

Structural complexities and sodium-ion diffusion in the intercalates NaxTiS2: move it, change it, re-diffract it

Abstract

After momentary attention as potential battery materials during the 1980s, sodium titanium disulphides, like the whole Na–Ti–S system, have only been investigated in a slapdash fashion. While they pop up in current reviews on the very subject time and again, little is known about their actual crystal-structural features and sodium-ion diffusion within them. Herein, we present a short summary of literature on the Na–Ti–S system, a new synthesis route to Na0.5TiS2-3R1, and results of high-temperature X-ray and neutron diffractometry on this polytype, which is stable for medium sodium content. Based thereon, we propose a revision of the crystal structure reported in earlier literature (missed inversion symmetry). Analyses of framework topology, probability-density functions, and maps of the scattering-length density reconstructed using maximum-entropy methods (all derived from neutron diffraction) reveal a honeycomb-like conduction pattern with linear pathways between adjacent sodium positions; one-particle potentials indicate associated activation barriers of ca. 0.1 eV or less. These findings are complemented by elemental analyses and comments on the high-temperature polytype Na0.9TiS2-2H. Our study helps to get a grip on structural complexity in the intercalates NaxTiS2, caused by the interplay of layer stacking and Na–Ti–vacancy ordering, and provides first experimental results on pathways and barriers of sodium-ion migration.

Graphical abstract: Structural complexities and sodium-ion diffusion in the intercalates NaxTiS2: move it, change it, re-diffract it

Supplementary files

Article information

Article type
Paper
Submitted
23 Jul 2019
Accepted
25 Aug 2019
First published
03 Sep 2019
This article is Open Access
Creative Commons BY license

RSC Adv., 2019,9, 27780-27788

Structural complexities and sodium-ion diffusion in the intercalates NaxTiS2: move it, change it, re-diffract it

D. Wiedemann, E. Suard and M. Lerch, RSC Adv., 2019, 9, 27780 DOI: 10.1039/C9RA05690D

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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